Strange cavity walls?

[poddy1967]

Trying so sort out a damp problem in our kitchen. We had the house wall-lagged a few years ago (don't by the way!) and since then suffered terrible condensation. Anyway, back wall of kitchen also appears to be drawing in damp so decided to take a couple of bricks out to see if insulation material's wet.

Took out 2 bricks. We have a rendered house, only the first few rows of bricks visible. Anyway, expected to find cavity but there isn't, it's solid? Cavity only starts after next row, so 2 rows above DPC? The next row of bricks are set back about half an inch and render makes wall level with base bricks, a small step in other words if that makes sense?

Anyone heard of this type of construction before? Only appears to be that part of the house, it has no air bricks, unlike the rest of the house and now understand why. We believe in the past that this part of the house was originally some sort of semi-connected out-house used for coal but at some point was all connected up to house to extend kitchen.

Also anyone know of a company that can extract the insulation material from the walls?

 

[TerenceQ]

How old is the house, post war, inter war?

I've seen houses built in the 20's like this had one who had a dpc injected and the inside of the house smelt like a bitumen factory. Turned out the solid portion was dressed inside with bitumen to keep out damp and the injected dpc "softened" the bitumen.

Air bricks should only be present if you have a suspended timber floor. Do you?

The clear cavity was probably allowing damp to evaporate now it has nowhere to go except to internal wall. I am guessing the render is sand and cement so least line of resistance is inside as it is either porous block or "weaker" brick than external leaf.

Similar problem happens when the dry lining is taken off the internal walls of victorian houses and replaced with solid plaster. There is an expected amount of moisture which will disperse with no affect behind the dry lining, take that away and all off a sudden you have rising damp.

Terry

 

[poddy1967]

How old is the house, post war, inter war?

I've seen houses built in the 20's like this had one who had a dpc injected and the inside of the house smelt like a bitumen factory. Turned out the solid portion was dressed inside with bitumen to keep out damp and the injected dpc "softened" the bitumen.

Air bricks should only be present if you have a suspended timber floor. Do you?

The clear cavity was probably allowing damp to evaporate now it has nowhere to go except to internal wall. I am guessing the render is sand and cement so least line of resistance is inside as it is either porous block or "weaker" brick than external leaf.

Similar problem happens when the dry lining is taken off the internal walls of victorian houses and replaced with solid plaster. There is an expected amount of moisture which will disperse with no affect behind the dry lining, take that away and all off a sudden you have rising damp.

Terry

Thanks Terry,

Was built in 1930 and has sand/cement render and yes I believe the DPC is bitumen type as in places you can see what looks like melted black plastic protruding from the mortar.

I have now accessed the cavity higher up and the inside face of the outside wall is very damp. Strangely can't see any cavity insulation in this bit of the wall, although I can only see a small bit of the cavity.

All of the house except this small part has air bricks top and bottom but we have concrete floors. The house is of unusual construction as it was originally all flat-roofed (6 inch thick concrete). We have since fitted a normal roof over this but that might be why it had air bricks?

I think probably we just need more ventilation, we're about to have new double glazing fitted, which I guess will only make things worse in terms of condensation but I suppose we could get them with vents although I always think that defeats the object.

 

[TerenceQ]

You can buy a little stick on block which you adhere to the wall, leave it over night and it will tell you if it is condensation, can't remember where to buy them though, try checking out survey equipment suppliers.

I am guessing it is more likely to be condensation based on the type of construction you describe. Many of this "system" built housing gave problems of condensation when the were upgraded, usually by a retro-fit of as rendered block cavity outer leaf.

Rather than putting vents everywhere look at fitting a "Drimaster"

 

[dormermike]

I've seen houses built in the 20's like this had one who had a dpc injected and the inside of the house smelt like a bitumen factory. Turned out the solid portion was dressed inside with bitumen to keep out damp and the injected dpc "softened" the bitumen.

Hi Terry - sorry to hijack a thread but i couldnt work out how to PM you.

My bungalow has two bedrooms (front bay rooms) which have a faint bitumen smell inside them. The house was "damp proofed" with injections back in 1994. Anything left on top of the parquet blocks takes on a bitumen smell. Very annoying. I've been searching the internet for the past two years. Sounds like you may be onto something?